Conceptual question on exception in S04

[John M. Dlugosz]

I'm trying to work out some details of this area, but I don't understand what S04 is 
trying to say.  Could someone please point me in the right direction?  I'd be happy to 
then edit the S04 to contribute.

In S04, the "Exceptions" section mentions that $! contains multiple exceptions.
 So what type is it?  Why isn't it @! ?  I says that they are thrown as a
single new exception.  So what type is that new exception?  A multi-exception of
some kind?

How do you get multiple pending exceptions in the first place?

If you mean that exceptions can be thrown (and handled) within the handling of
another exception, then the list should be more of a stack.  Should the handler
then see the topmost one as its topic?  If you really did make the whole list
the topic then it would be difficult to match.

How would you access the other exceptions in $!, presumably testing them for
.defined etc.?

Granted that the paragraph is muddled due to old edits from previous ideas, I'd
be happy to rewrite it.  But what =is= the current central concept that it is
trying to explain?

--John